Diagnosing anemia, a condition defined by low red blood cell count that can represent iron deficiency, is straightforward enough in much of the world. Doctors do so by drawing a blood sample to take stock of hemoglobin levels, the protein found within the blood cells, but in places without such access to health care it often goes undiagnosed. This can lead to dangerous complications that include severe fatigue, heart problems and death. Looking to tackle this problem, scientists have developed an app that accurately measures hemoglobin levels in a patient using the phone's camera and flash, raising the prospect of a low-cost, non-invasive screening tool for the condition.

The versatility of the smartphone has made it a hugely useful tool for our day-to-day activities, and its multipurpose functionality is proving a game-changer in the world of medicine, too. Researchers have harnessed smartphone technology to develop mobile pregnancy tests, sleep apnea detectors and cheaper stethoscopes, the type of advances that could have real ramifications in the developing world.

"In developing countries, community health workers have so much specialized equipment to monitor different conditions that they literally have whole bags full of devices," says electrical engineering doctoral student at the University of Washington (UW), Edward Wang. "We are trying to make these screening tools work on one ubiquitous platform – a smartphone."

Wang led a team of electrical engineers and computer scientists in developing HemaApp, a smartphone app that uses the device's flash to blast the patient's finger with various wavelengths of light, and then the camera to capture the color of the glowing fingertip. Because blood plasma and hemoglobin absorb light at different wavelengths, by assessing the color of the resulting glow through special algorithms HemaApp can make an estimation of the hemoglobin concentration within.

In a trial with 31 patients, the team found that HemaApp had a 69 percent correlation to the patient's blood test, the gold standard for accuracy. But they also tested its performance when used in conjunction with additional light sources, conditions the researchers say replicate the infrared and multi-color LED capabilities of modern and yet-to-be-developed smartphones. It found that when used under a common incandescent light globe, it produced a 74 percent correlation to the blood test, while using a set of LED lights instead upped the accuracy to 82 percent.

The results were comparable to the Masimo Pronto, a more costly medical device currently used to non-invasively measure hemoglobin levels by clipping onto the person's finger, which produces an 81 percent correlation to the blood test. Using just the smartphone's camera, HemaApp correctly detected low hemoglobin levels 79 percent of the time, and with extra light sources, 86 percent of the time.

As such, HemaApp is not positioned as a replacement for a blood test as a diagnostic tool, but rather as an early screening tool for anemia.

"Anemia is one of the most common problems affecting adults and children worldwide," says co-author Doug Hawkins, a UW Medicine, Seattle Children's Hospital and Seattle Cancer Care Alliance pediatric cancer specialist. "The ability to screen quickly with a smartphone-based test could be a huge improvement to delivering care in limited-resource environments."

From here, the team plans to carry out further testing of the app, gather data to boost its accuracy and expand its uses to detect specific blood disorders that arise from low hemoglobin.

The paper describing the research can be accessed online, and you can see how the app works in the video below.